interface CompurerAverage {
	public double average(double a,double b);
}
class A implements CompurerAverage {
	public double average(double a,double b) {
		double aver=0;
		aver=(a+b)/2;
		return aver;
	}
}
class B implements CompurerAverage {
	public double average(double a,double b) {
		double aver=0;
		aver=Math.sqrt(a*b);
		return aver;
	}
}
public class Example6_4 {
	public static void main(String args[]) {
		CompurerAverage computer;
		double a=11.23,b=22.78;
		computer = new A();  
		double result = computer.average(a,b);
		System.out.printf("%5.2f和%5.2f的算术平均值:%5.2f\n",a,b,result);
		computer = new B();  
		result= computer.average(a,b);
		System.out.printf("%5.2f和%5.2f的几何平均值:%5.2f",a,b,result);
	} 
}
